This application claims the priority of German application 196 25 553.8 filed in Germany on Jun. 26, 1996, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a device for the centric and/or imbalance-free holding of workpieces or tools on a spindle of a machine tool by means of centric holding surfaces.
For example, in turning machines having a spindle, tools are received in exchangeable clamping sleeves or workpieces to be machined are received in clamping chucks and these, in turn, are received in holding devices of the spindle on cylindrical holding or clamping surfaces which are centric with respect to the axis of rotation of the spindle. Also, in the case of a high-precision manufacturing, these holding or clamping surfaces have an unavoidable eccentricity with respect to their axis. When receiving a tool in a clamping sleeve or a workpiece in a clamping chuck and the clamping sleeve or the clamping chuck in the spindle, these eccentricities are added up depending on the respective accidental angular position of the parts in a mutually reinforcing or reducing manner.
In other cases, the mentioned parts also have unbalanced masses which, when being received in the spindle, also add up in a reinforcing or reducing manner and, particularly, in the case of high rotational speeds, lead to vibrations or machining faults.
It is an object of the invention to provide a simple possibility for rapidly inserting a tool in a clamping sleeve, a workpiece in a clamping chuck and a clamping sleeve or a clamping chuck in a spindle of a turning machine and removing it and holding it securely.
The invention achieves this object by providing an arrangement of the above-mentioned type wherein device holding surfaces are provided with profiles which are coordinated with one another in pairs and which each have at least two wedges which rise over imaginary cylindrical reference surfaces radially toward the outside or toward the inside and each again drop steeply back to the reference surfaces, are offset by the same angles in the circumferential direction and have a joining gap in a joining position.
Because of the joining gap and the wedges arranged around the circumference of the holding surfaces, the tool can be inserted in the clamping sleeve, the workpiece can be inserted in the clamping chuck and these can, in turn, be inserted in the spindle and by a rotating about a fraction of a rotation can be fastened by means of a frictional engagement.
Particularly when three wedges are arranged to be offset with respect to one another by the same angles, a very good centering effect can be obtained.
In particular, when the number of the wedges is increased to, for example, six, there is the advantage that, in the angularly offset starting positions corresponding to the number of wedges the parts are inserted into the respective assigned holding device and are connected with it in a frictionally engaged manner by rotating. In the case of a flat slope, a rotational frictional engagement of up to 30.degree. is possible. In the case of, for example, six wedges on the circumference, six different positions are obtained for the fastening which each extend over up to 30.degree.. When the angular positions of the eccentricities or unbalanced masses of two respective parts to be connected are known with respect to a respective starting position, the parts can be joined in such a mutual angular position and rotated into the frictional engagement that the eccentricities or unbalanced masses are largely diametrically opposite with respect to the axis of rotation of the spindle. As a result, it is achieved that the eccentricities or the unbalanced masses compensate one another as much as possible up to a remaining minimum.
The minimal number of wedges around the circumference of the holding surfaces is two--which ensures a secure holding and, particularly when the surfaces of the wedges according to the invention follow the course of a logarithmic spiral and are therefore disposed flatly against one another in all angular positions with respect to one another, offers a high centering precision in the respective holding device.
The flatter the slope of the wedges in the profile pairings, the larger the angle about which the parts in the frictional engagement can be rotated into a position of an optimal compensation of the eccentricities or of the unbalanced masses.
The width of the wedges is selected such that the required torque can be sensed and transmitted during the work of the tool or during the machining of the workpiece. The slope direction of the wedges is advantageously such that the frictional engagement has the tendency of being increased during the machining.
Furthermore, the wedge-shaped profiles have the advantage that they act as an overload protection particularly during the holding of a tool. Specifically, if the slope of the wedges and/or the length of the wedges is low in the circumferential direction, the wedges may jump over in the case of an extreme rise of the moment of resistance; that is, the highest elevations of the wedges of a profile pairing slide over one another. This limits the rise of the contacting moment and a break is avoided.
It is preferably provided in this case to displace a jumping-over of profile pairings between a tool and the clamping sleeve by correspondingly selecting the slopes in order to avoid damage to the holding device on the spindle.
An advantageous slope of the wedges depends, among other things, on the diameter of the profiling. When the diameters are small, the slopes are higher and are in the range of from 1:50 to 1:200. When the diameters are large, the slopes may be reduced to 1:500.
The figures of the drawing schematically show the embodiments of the invention on a turning machine and in the form of a clamping chuck, a clamping sleeve and a tool. It is understood that the invention can also be used on many other devices.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.